Nokia Lumia 920 - Why can I not see my 5GHz WiFi access point during flight (airplane) mode?

The reason that the 5GHz WiFi band is disabled during flight (airplane) mode is comply with local regulations. There are regions in the world where the usage of the 5GHz band is not allowed to be used for WiFi transmissions. As the Lumia WP8 phones are unable to determine the location whilst in flight mode, the phones disable the usage of the 5GHz WiFi band in order to comply with regulations.